1. Field of the Invention
The present invention relates to a method of detecting a specific object region and digital camera. More particularly, the present invention relates to a method of detecting a specific object region and digital camera in which the specific object region is detected according to image data, and in which an amount of a task of arithmetic operation and memory resource can be reduced.
2. Description Related to the Prior Art
U.S. Pat. No. 4,203,671 (corresponding to JP-A 52-156624), U.S. Pat. No. 4,244,654 (corresponding to JP-A53-145621) and U.S. Pat. No. 4,244,655 (corresponding to JP-A53-145622) disclose a method of detecting portions of flesh color from an original image as detection of a facial image region from the image, to determine a facial image from a collected portion of photometric points in a region in the flesh color. U.S. Pat. No. 5,278,921 (corresponding to JP-A 4-346333) discloses a method of detecting a facial image region by conversion of photometric data into information of hue and chroma, to create and analyze a histogram of two dimensions. JP-A 8-063597 discloses a method of deriving candidate regions of facial image regions by considering a human facial shape so as to determine a facial image region according to characteristic values in the candidate regions.
In any of those methods, the total of each image must be processed by image processing for the purpose of recognizing a specific object in the image. Even CPU or calculating devices with high performance require long time, because the amount of the calculation is considerably great.
JP-A 2001-116985 discloses a camera and object recognition. The camera includes an object recognition unit, a visual line recognition unit, a visual line detector and an image cropping unit. The object recognition unit recognizes an object. The image cropping unit determines a recognizing position and range of the object recognition unit according to outputs from the visual line recognition unit and the visual line detector. The object recognition unit and the image cropping unit cooperate to determine the position of the object to recognition at a high speed and high precision.
JP-A 2004-171490 discloses a method in which the irrelevant images and the target images are predetermined. The irrelevant images are among a plurality of consecutive picture frames, and are eliminated from consideration in which a specific object is searched. The target images are among the plural consecutive picture frames, and are searched as a target for detecting the specific object. The target images are sequentially arranged between two or more of the irrelevant images at a predetermined period, to reduce the total of the task of arithmetic operation. After one of the target images of which the specific object is detected, points located close to the detected specific object are searched, which is effective also in reducing the total of the task.
However, there remain problems in those known methods. In JP-A 2001-116985, an error may occur in the object recognition of a principal object typically when two or more object exist. Failure occurs when the principal object is offset from the position of the visual line of recognition. In JP-A 2004-171490, a problem is caused by the process of thinning itself. The target images are handled in the widely known manner, so that there is no reduction of the task of the calculation. The problem of JP-A 2001-116985 remains also with JP-A 2004-171490 in relation to the points close to the specific object.